The present application claims priority upon Japanese Patent Application No. 2001-288833 filed on Sep. 21, 2001, which is herein incorporated by reference.
1. Field of the Invention
The present invention relates to a data processing system comprising a host processing device and a storage control device connected to the host processing device via a communication means and storing data sent from the host processing device, and the storage control device using this data processing system. In particular, the present invention relates to a technique for assigning an alias device to a base device in order to maximize the effect of the alias device from a viewpoint of the entire processing of the data processing system, in a mechanism where, in case the host processing device conducts an I/O process to a certain logic device (hereinafter referred to as xe2x80x9cbase devicexe2x80x9d) and a control block assigned to the logic device (hereinafter referred to as xe2x80x9cbase control blockxe2x80x9d) is in use thereupon, the process is conducted by a control block (hereinafter referred to as xe2x80x9calias control blockxe2x80x9d) assigned to another logic device (hereinafter referred to as xe2x80x9calias control blockxe2x80x9d).
2. Description of the Related Art
In a data processing system constructed by connecting a host processing device, such as a main frame, and a storage control device, such as a disk array device, when an I/O request is conducted to the storage control device from the host processing device, the host processing device designates an actual storage region, which is to be a target of processing, by a logic device which is defined to correspond with the actual storage region, and conducts this processing by a control block (hereinafter referred to as xe2x80x9cbase control blockxe2x80x9d) assigned one to one to the logic device.
Here, in a general conventional data processing system, only one base control block could be assigned to the I/O processing of the certain logic device. Thus, for example, when the I/O request continuously occurs in respect to the certain logic device, a processing of the next I/O request could not be conducted until the processing of the previous I/O processing was completed, thereby causing a waiting time at the host processing device to occur.
In order to solve these inconveniences, for example, U.S. Pat. No. 5,530,897 discloses a mechanism where, in a case a base control block (in the above document, xe2x80x9cUnit Control Blocksxe2x80x9d corresponds to control block) of a certain logic device (hereinafter referred to as xe2x80x9cbase devicexe2x80x9d) is in use, the I/O request is processed by a control block (hereinafter referred to as xe2x80x9calias control blockxe2x80x9d) made to correspond to another logic device (hereinafter referred to as xe2x80x9calias devicexe2x80x9d) assigned to the logic device.
Incidentally, since the number of alias devices defined between the host processing device and the storage control device is limited, it is ideal for the alias device to be assigned to the base device so the effect of the alias device may be exhibited to a maximum. Therefore, conventionally it was devised to make the effect of the alias device become as large as possible by methods such as in which a user predicts a processing load of each of the base control blocks and fixedly assigns the alias devices (i.e., static method), or in which the host processing device automatically assigns the alias devices according to the processing load of the base control block (i.e., dynamic method).
However, the assignment of the alias control blocks by the static method or the dynamic method is based on mainly circumstances of the host processing device such as a load state of the base control block, so that from the point of view of process efficiency of the entire data processing system comprised of the host processing device and the storage control device, there are many cases where assignment of the alias control block is not always optimized. For example, even if many alias devices are assigned to a base device with a high processing load, and waiting at the host processing device is decreased, if the I/O processing load in respect to a physical device of the storage control device is large, the effect of the alias control block from the viewpoint of the entire data processing system will be reduced.
The present invention is made in view of the above matters, and it is an object to provide a data processing system which may assign an alias device so an effect thereof is exhibited to a maximum from a point of view of improving process efficiency of the entire data processing system, and a storage control device using this data processing system.
In order to achieve this object, an aspect of the present invention is a data processing system comprising a host processing device, and a storage control device connected to the host processing device via a communication means and storing data sent from the host processing device, wherein: the host processing device and the storage control device specify, upon an I/O processing of data in respect to an actual storage region of the storage control device, the actual storage region which becomes a target of the processing by a logic device corresponding to the actual storage region; the host processing device comprises a plurality of control blocks processing an I/O request in respect to the storage control device, and comprises a means which, in a case an I/O request in respect to a certain logic device (base device) occurs, makes a control block (base control block) corresponding to the base device conduct a processing in respect to the I/O request, whereas, if the base control block is in use, makes a control block (alias control block) of another logic device (alias device) assigned to the logic device conduct the processing; the storage control device comprises a deciding means for deciding, upon processing an I/O request in respect to a certain logic device, whether or not there is a need to newly assign an alias device to the logic device according to a situation of one or a plurality of component elements within the storage control device, and a means for notifying the host processing device via the communication means to the effect that assigning is decided as necessary according to the decision; and the host processing device comprises a means for recognizing that an alias device is newly assigned to the base device when there is the notification from the storage control device.